I did it both ways...
1) Last year I found an old USGI stock on Heebay. It looked really rough, and I didn't know if it was 'worn out'.
I did a trial fit straight away. "Drop-in"?? Hah! It nearly
Fell in! But some range time assured me it'd be a good shooter, so I spent some time and effort to refinish it, and it came out looking pretty good--old and 'experienced', but still good looking.
2) Finally, Boyds had a sale on their M-14 stocks that put them under the import limiting pricetag, so I ordered both stock and handguard. Out of the box, my action dropped right in (
Yea!) but when it was closed up tight, it failed the all-important '
safety function test' (
Boo!). Of course I went straight to the 'Nutters' forum and conducted a search, which lead me here: http://www.canadiangunnutz.com/forum/showthread.php/91174-M14-M305-M1A-Test-after-assembly. I found Post #5 particularly informative. You don't want to remove too much wood, so be careful.
I also had to do "
the popsickle stick trick". I abandoned the
front sling swivel and ordered a new one from "Treeline".
The rest of the stock hardware transferred right over to the Boyds, no problemmo.
Before I put it all back together, I rubbed in two coats of
Pure Tung Oil. I will give it a third coat this winter.
2a) THE HANDGUARD: If you want to swap to the Boyds walnut handguard, your problems are not yet over.

I decided to abandon the
front ferrule as well, as my Norky plastic piece was in jeopardy of damage were I to attempt separating the two. Instead, I ordered a replacement ferrule from Treeline when I ordered the swivel.
That tapped onto the front of the Boyds handguard more easily than I expected, but
be careful here--that wooden
handguard is fragile and liable to split under harsh treatment.
I was able to >pop< to rear clip off the Norky after some fiddling with screwdriver and needle-nose pliers. There is a special tool specific to this purpose, but hardly worth it unless you change out clips frequently.
Before I was able to install the clip to the Boyds handguard, some minor trimming was required around the right-rear corner of the new handguard to allow for the op rod travel.
Also (now
be careful here!) the wooden handguard is thicker than the Norky plastic one, and may well break if you slap it down onto the receiver. You don't want that. What you need here is some judicious trimming of the inside/rear of the handguard so that it has just enough clearance to fit over without splitting. Once this is so, you can then install the clip and (gently) smack it into place where it may dwell in peace for all eternity.
That's it--Your new Boyds stock is installed around your rebuilt and fully functioning Norinco 305s/M14.
There are several methods for 'fine finishing' of the Boyds, the first of which is to leave it 'as-is' and say,
"It is finished!"